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RISS 인기검색어
- 검색키워드
- 저자 : Nobuyuki Umezu (검색결과 5 건)
- 무료
- 기관 내 무료
- 유료
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2D wavelet transform data compression with error level guarantee for Z-map models
Nobuyuki Umezu,Keisuke Yokota,Masatomo Inui 한국CDE학회 2017 Journal of computational design and engineering Vol.4 No.3
Most of workpiece shapes in NC milling simulations are in Z-map representations that require a very large amount of data to precisely hold a high resolution model. An irreversible compression algorithm for Z-map models using a two-dimensional Haar wavelet transform is proposed to resolve this tight memory situation for an ordinary PC. A shape model is first transformed by using Haar wavelet to build a wavelet synopsis tree while the maximum errors caused by virtually truncating high-frequency components are simultaneously calculated. The total amount of the shape data can be reduced by truncating particular sections of the wavelet components that satisfy the error threshold given by the user. Our algorithm guarantees that any error due to its irreversible compression processes is smaller than the specified level measured against the original model. A series of experiments were conducted using an Apple iMac with a 3.2 GHz CPU and 8 GB of memory. The experiments were performed with 16 sample shape models on 512?512 to 8192?8192 grids to evaluate the compression efficiency of the proposed method. Experimental results confirmed that our compression algorithm requires approximately 20–30 ms for 512?512 models and 7 s for 8192?8192 models under a maximum error level of 10? 10?6 m (a typical criteria for NC milling simulations). The compressed binaries outputted by the proposed method are generally 25–35% smaller than the baseline results by gzip, one of common reversible compression libraries, while these two methods require almost the same level of computational costs.
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A Dexel Based Algorithm for Evaluating Thickness of Solid Models (ACDDE 2010)
Satoru Yamazaki,Nobuyuki Umezu,Mastomo Inui (사)한국CDE학회 2010 한국CAD/CAM학회 국제학술발표 논문집 Vol.2010 No.8
In the current manufacturing practice, injection molding is widely used for fabricating plastic parts of various consumer products such as digital cameras, printers, and other electric appliances. In designing a plastic part, thickness of the part should be constant all over the surface, otherwise some deformations happen in the molding process which deteriorate the aesthetic quality of the product. In this paper, the authors propose a fast algorithm for evaluating the thickness of the solid model. Most commercial CAD systems provide some kinds of thickness measuring functions of solid models, these functions, however, are not appropriate for evaluating thickness of the complex shape. In this paper, a new definition of the thickness of the solid model is proposed. Based on the definition, a dexel based thickness evaluation algorithm is developed. A depth peeling based method for converting a boundary representation solid model into a solid model in the dexel representation is also proposed. A system is implemented and some computational experiments are performed.
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Automatic Detection of the Optimal Ejecting Direction Based on a Discrete Gauss Map
Masatomo Inui,Nobuyuki Umezu,Hidekazu Kamei (사)한국CDE학회 2013 한국CAD/CAM학회 국제학술발표 논문집 Vol.2010 No.8
In this paper, the authors propose a system for assisting mold designers of plastic parts. Plastic parts are usually produced by the injection molding. In this method, the formed part must be removed from the mold core in a single ejecting direction. With a CAD model of a part, the system automatically determines the optimal ejecting direction of the part with the minimum undercuts. Two methods are introduced for improving the performance and the accuracy of the authors’ prior system. New point distribution method for the discrete Gauss map is adopted which is based on the architectural geodesic dome concept. Hierarchical structure is also introduced in the point distribution, a higher level “rough” Gauss map with sparse point distribution and another lower level “fine” Gauss map with much dense point distribution. By using this discrete Gauss map representation, a new algorithm is developed for computing the optimal ejecting direction. An experimental system is implemented and computational experiments are performed. Our system needs less than 30 seconds for determining the optimal ejecting direction of a CAD model with more than 1 million polygons.
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Automatic detection of the optimal ejecting direction based on a discrete Gauss map
Inui, Masatomo,Kamei, Hidekazu,Umezu, Nobuyuki Society for Computational Design and Engineering 2014 Journal of computational design and engineering Vol.1 No.1
In this paper, the authors propose a system for assisting mold designers of plastic parts. With a CAD model of a part, the system automatically determines the optimal ejecting direction of the part with minimum undercuts. Since plastic parts are generally very thin, many rib features are placed on the inner side of the part to give sufficient structural strength. Our system extracts the rib features from the CAD model of the part, and determines the possible ejecting directions based on the geometric properties of the features. The system then selects the optimal direction with minimum undercuts. Possible ejecting directions are represented as discrete points on a Gauss map. Our new point distribution method for the Gauss map is based on the concept of the architectural geodesic dome. A hierarchical structure is also introduced in the point distribution, with a higher level "rough" Gauss map with rather sparse point distribution and another lower level "fine" Gauss map with much denser point distribution. A system is implemented and computational experiments are performed. Our system requires less than 10 seconds to determine the optimal ejecting direction of a CAD model with more than 1 million polygons.
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Visualization of potential sink marks using thickness analysis of finely tessellated solid model
Masatomo Inui,Shunsuke Onishi,Nobuyuki Umezu 한국CDE학회 2018 Journal of computational design and engineering Vol.5 No.4
Sink marks are unwanted shallow depressions on the molded plastic surface caused by localized shrink-age during the hardening process of injection molding. Sink marks appearing in the exterior impair the aesthetic quality of the product. In this study, a novel method for extracting potential sink marks that can occur on the part surface is proposed. The thicker portion of the part shrinks with a greater amount than that of the thinner portion. This difference in the shrinkage amount is the main cause of the sink mark. In the plastic part design practice, engineers often check the thickness distribution to predict potential sink marks in the part surface. Our method can be considered as an automated technique of such manual inspection task. A polyhedral solid model of the part with sufficiently small triangles of nearly the same size is prepared. The amount of shrinkage at each polygon is estimated based on its thickness and the shrinkage ratio of the part. The developed algorithm extracts the potential sink marks by analyzing the shrinkage distribution on the part surface.
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